The present invention relates generally to a continuous coating apparatus and method. More particularly, the invention is directed to a cord coating apparatus and a method for the continuous coating of thin layer of viscous materials on a moving cord or filament.
Coatings of 1-2 xcexcm and less are needed for the treatment of the tire cord and wires to improve tire durability, wire-rubber interfacial bonding, and corrosion aging resistance. It is known to use a continuous method to produce coated wires using apparatus consisting of a coating die which surrounds a wire and an extruder that extrudes coating material into the die around the wire. In industry, such an apparatus has been used in the coating of insulating material around electrical conducting wire where the needed coating thickness was 1 mil and thicker. However, the needed coating of 1-2 xcexcm and less for the tire cord surface treatment is impossible to apply by conventional extrusion die coating process.
In another known continuous method to control the coating thickness of tire cord down to 1-2 xcexcm or less, an air-wipe is used that wipes off excess coating materials right after a conventional dip-coat procedure. However this method is mainly employed to control the thickness of water base latex coat of a low viscosity coating material. For a high viscosity coating material such as an oil base mixture having a viscosity of 100 SUS and higher, the conventional dip-coat with air-wipe method is very difficult to operate and control. Additionally, the air-wipe which uses a strong air blast to wipe off the excess coating may limit the penetration of the coating material into the inner cord because of the volume expansion of the trapped air inside the cord according to the Bernoulli principle of physical matter.
The advantages of the present invention are numerous and are as follows.
The invention provides an apparatus and method which can be utilized to apply a thin layer of viscous coating material to an elongated continuously moving filament whereby the filament can be cabled, coated, and spooled in a continuous operation.
The invention provides an apparatus and method for applying a thin layer of latex base coating material to a continuously moving cord for an improved coating penetration.
The invention provides an apparatus and method for applying a thin layer of coating material with a high coating efficiency.
The invention provides an apparatus and method that can be utilized to improve cord coating at processing speeds that are limited only by the pay-off and the wire take-up services.
The invention provides an apparatus and method which optimized the coating mist typically associated with coating operations, thereby reducing the cost of the pollution control equipment and the recycling of excess coating materials.
The invention provides an apparatus and method that eliminates the need for highly complex machinery.
The present invention provides an improved wire manufactured by a technique having all the advantages of a conventional wire process but none of the disadvantages.
The disclosed apparatus has a coating material applicator to deliver a flowable material, an air applicator to supply compressed air, a mixer to mix the flowable material and compressed air, a delivery means to spray the mixed flowable material and air onto a filament, and a coating chamber through which the filament passes. The chamber has a material collector and a coating die, and a sealing attachment with an exit hole is located beneath the coating chamber. The filament is sprayed before it travels into the material collector.
In one aspect of the invention, the coating material applicator is selected from the group consisting of a constant volume material ejector, an intermeshing positive displacement multi-screw delivery pump, and a gear pump.
In one aspect of the invention, the delivery means is inclined at an angle relative to the coating chamber and the lowermost end of the delivery means is adjacent to the material collector.
In another aspect of the invention, the sealing attachment is shaped to form a spherical cone with the hole at the apex, forming an open area through which the filament passes.
In another aspect of the invention, the coating chamber dimensions can be varied. For example, the top entrance of the coating chamber may have a diameter larger than the main portion of the coating chamber and the exit of the coating chamber may have a diameter less than the coating die.
In another aspect of the invention, the coating chamber is mounted on a frame capable of linear movement relative to a take-up spool. This helps to ensure smooth and even spooling of the coated filament.
In another aspect of the invention, the material collector has an interior converging wall to permit collection of any stray flowable material.
In another aspect of the invention, the coating chamber has a vertical orientation. The vertical orientation of the chamber assist the flow pattern of the flowable material as it is sprayed onto the moving filament and in forming a small volume dip bath through which the filament may pass.
In another aspect of the invention, a cabling device is operatively associated with the coating apparatus.
Also disclosed is a method of coating a filament with a flowable material. The method includes the steps of providing a flowable material, providing compressed air, mixing the flowable material and the compressed air, spraying the mixing flowable material and compressed air onto a moving filament to coat the filament, and passing the filament through a material collection die, a coating die, and an exit hole having a diameter not more than the diameter of the filament.
In another aspect of the method, the filament passes through an open area prior to passing through the exit hole.
Also disclosed is a method of applying a coating of less than 2 xcexcm on a moving filament. The method includes the steps of moving a filament along a defined travel path, providing a mix of a flowable material and a compressed air, spraying the flowable material and compressed air onto the moving filament, passing the filament through a small volume dip pool, and pulling the filament through a hole having a diameter not more than the diameter of the filament.
In one disclosed aspect of the method of applying a coating of less than 2 xcexcm on a moving filament, the small volume dip pool has a volume of not more than 1.0 cc of liquid.
In another aspect of the method of applying a coating of less than 2 xcexcm on a moving filament, there is the further step of passing the filament through an open area after passing the filament through the small volume dip pool and before pulling the filament through the hole.
In both methods disclosed, the filament may be formed of either steel or an organic material.